Alkylation of isoparaffins



Feb. 29, 1944. c. B. LINN 2,342,677

ALKYLATION 0F ISOPARAFFINS Filed Nov. 16, 1942 Patented Feb. 29, 1944 ALKYLATION F ISOPARAFFINS Carl B. Linn, Riverside, lll., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application November 16, 1942, Serial No. 465,692

(Cl. 260-683A) 18 Claims.

This application is a continuation-impart of my co-pending application Serial No. 402,273 filed July 14, 1941.

This invention relates to the alkylation of parafllnic hydrocarbons. It is more specifically concerned with a process for the production o f high antiknock motor fuel in which isoparaflins, particularly lsobutane and isopentane, and mono oleflnic hydrocarbons, particularly those having 3. 4, and 5 carbon atoms per molecule, are effectively converted into higher molecular weight hydrocarbons of gasoline boiling range in the presence of a hydrogen fluoride catalyst.

The invention also involves a novel method for the regeneration of the used catalyst whereby purified hydrogen fluoride is recovered and returned to the alkylation step of the process.

In one broad embodiment the present invention relates to a method of regenerating contaminated hydrogen fluoride catalyst from an isoparallin-olefin alkylation process which comprises diluting said contaminated catalyst with water whereby to separate organic contaminants from an aqueous hydrogen fluoride layer, with.- drawing said organic contaminants from the system, reacting said aqueous hydrogen fluoride with olefins under hydro'fluorinating conditions whereby to convert a. substantial amount of said hydrogen fluoride to alkyl fluorides, and returning said alkyl iluorides to the alkylation step.

In a more specific embodiment the invention relates to a process for eecting the alkylation of paraflinic hydrocarbons which comprises the steps of reacting olefinic hydrocarbons with isoparaillnic hydrocarbons under alkylating conditions in the presence of a hydrogen uoride catalyst, separating hydrocarbon reaction products from the bulk of the used hydrogen fluoride catalyst, fractionating said hydrocarbon reaction products to recover desired alkylation products, diluting at least a portion of said separated used hydrogen fluoride catalyst with water whereby to separate organic contaminants from aqueous hydrogen fluoride, withdrawing said organic contaminants from the system, reacting atl least a portion of said aqueous hydrogen fluoride with. oleflnic hydrocarbons under hydrofluorinating conditions whereby to form alkyl fluorides, and introducing said alkyl fluorides into said first named alkylation step whereby free hydrogen fluoride is produced by the interaction of said isoparailinic hydrocarbons and said alkyl halides.

When concentrated or nearly anhydrous hydrogen fluoride is employed as the active catalytic agent in the alkylation of hydrocarbons in a continuous operation wherein used catalyst is separated from the hydrocarbon reaction products in a settling zone and returned to the alkylation zone, the catalyst phase gradually becomes contaminated with an organic fluorine-contaiu-v zone, one molecule of hydrogen fluoride is generated in situ as shown yby the following'r equation:

The regeneration method of this invention may u be applied to a conventional isoparaflln-oleiln alkylation process using a hydrogen fluoride catalyst, orit may also be incorporated into a twostage alkylation process involving the following steps: (1) the hydrofluorination of olefins with hydrogen fluoride to form alkyl fiuorldes, and (2) the reaction of isoparafns with said alkyl `fluorides in the presence of a hydrogen fluoride catalyst t0 form higher molecular weight isoparainic hydrocarbons.

The hydrofluorination of olefins in the first step of the above mentioned two-stage process may be conveniently carried out by employing the dilute or aqueous hydrogen fluoride obtained in the regeneration method of the present invention. Al-

though concentrated or nearly anhydrous hydrogen fluoride may be reacted with olefins to 'form alkyl fluorides at a temperature of from about to about 100 C., or preferably from about -30 to about 0 C., it has'been determined that more selective hydrofluorination is obtained when aqueous hydrogen fluoride is employed, especially V presence of a hydrogen u carried out at a temperature of from about -30 to about 100 C. and more preferably from about to about 50 C. PressureA has been found to have little eifect on the reaction but it should preferably be suiiicient to compensate for the vapor pressure of the reactants and maintain in v a substantial portion of the reactants liquid phase y the alkylation reand catalyst. By carrying out action so that a molar excess of isoparaiiin over olens and/or alkyl fluorides is present, for example, a molar ratio of from about 2:1 to about :1 or higher, the formation of polymers is substantially avoided with the result that there is a selectively high conversion of the reactants into alkylated paraiiinic hydrocarbons. The time factor in the alkylation step may be conveniently expressed in terms of:space time which is defined as the volumes of liquid catalyst in the alkylation zone divided by the liquid volume charge rate per minute of hydrocarbon reactants. The space time may vary from about 5 to about 80 minutes although the exact value chosen will depend upon the nature of the charging stock, the other operating variables, etc. In certain cases, it may be desirable to extend this range in either direction.

The drawing illustrates diagrammatically a ilow sheet of the steps involved in one embodiment of the present invention. The details of the apparatus which may be used in each of the steps have not been shwn since it is believed that these features are well-known to those skilled in the alkylation art.

Referring to the drawing,zone 3 represents a conventional alkylation reaction zone which may be mechanically agitated mixing zone or other form of apparatus wherein intimate contact can be obtained between the catalyst and hydrocarbon reactants. A butane-butene fraction is introduced through line I and line 2 into alkylation zone 3. 'I'he isoparaidnic reactant which, in this case may comprise isobutane, is charged through line 4 to the alkylation zone 3. Hydrogen fluoride catalyst is introduced by means of line 5. The `total reaction mixture or hydrocarbon-catalyst emulsion or any desired portion thereof passes through line 6 to separation zone 'I which ordiarily comprises a simple gravity settler. The v`pper hydrocarbon reaction products layer from zone 'I is. withdrawn through line 8 and introduced into fractionation zone 9 which ordinarily will comprise a plurality of fractionators wherein desired alkylation products may be separated from undesired products and unconverted reactants. The alkylation reaction products along with unconverted normal butane are removed through line I0, and unreacted isobutane is recycled by means of line II and line 4 to the alkylation zone 3. Propane or other light gases may be withdrawn from the system by means not l shown. The lower used hydrogen iiuoride catalyst layer is withdrawn from settling zone 1 through line I2 and a substantial portion thereof is preferably recycled through line I3 to line 5 and then to the alkylation zone 3. A portion of this used catalyst, however, is passed continuously or intermittently through line I2 to a catalyst recovery step hereinafter described in greater detail.

which contains from about 60 to about 80% by.

l weight of hydrogen iluoride. The step of diluting the contaminated hydrogen fluoride causes the hydrocarbonaceous contaminants to separate out, and when the aqueous mixture is passed through line I6 to a settling zone I'I the organic contaminant layer may be readily withdrawn through line I8. The aqueous hydrogen iluoride layer is withdrawn through line I9 'and may be treated by any of several alternative procedures. y

A portion or all of the dilute hydrogen fluoride is introduced by means of line 20 and line 2I into a hydroiiuorination zone 22. Additional quantities of dilute hydrogen fluoride may be added from an extraneous source through line 2| if desired. Olenic hydrocarbons, in this case a portion of the butane-butene fraction hereinbefore referred to, are introduced by means of line I into zone 22. It will be apparent that an oleiin-containing fraction from any other convenient source may be employed in zone 22 with substantially the same results. In the hydrofiuorination zone 22, the aqueous hydrogen iiuoride (preferably of 60 to `80% concentration) reacts with the butenes or other oleiins introduced thereto to form alkyl fluorides. The total reaction products from the hydroiiuorination zone 22 are passed through line 23 to a separation zone 24 which may conveniently comprise a settling zone. The alkyl fluorides are predominantly soluble in the hydrocarbon layer, i. e., the unconverted paraiiins or other hydrocarbons which were introduced into zone 22 as components of the butane-butene fraction or other olefin-containing fraction charged thereto. The hydrocarbon layer from zone 24 comprising alkyl fluorides dissolved in unconverted hydrocarbons is charged to the alkylation zone 3. The isobutane charged to alkylation zone 3 is, therefore, alkylated with alkyl iiuorides introduced from line 25 and also with olens introduced from line 2. During the reaction of the alkyl iluorides with isoparaflins. hydrogen fluoride is generated in situ and becomes available as a catalyst for the alkylation reaction as hereinbefore described. The aqueous layer from separation zone 24 is withdrawn through line 26 and is preferably passed by means of line 21 and line 28 to the dilution zone I4. In many cases this aqueous layer may contain appreciable quantities of unconverted hydrogen uoride.

If desired a portion of the dilute hydrogen fluoride layer withdrawn from zone Il through line I9 may be introduced into a fractionation zone 29 wherein anhydrous hydrogen fluoride is distilled overhead from a hydrogen fluoridewater mixture having a lower hydrogen iluoride concentration which may be withdrawn through During the course of the reaction in alkylation A line '30. This mixture will ordinarily comprise a ide may be diverted through line 32 to line 20 and thus introduced into the hydrofluorination zone 22. This alternative provides a means for controlling the hydrogen fluoride concentration of the aqueous hydrogen fluoride introduced into zone 22. In the event that the aqueous layer from separation zone 24 contains appreciable quantities of uncoverted hydrogen fluoride, it may be desirable to pass a portion of this layer directly through line 26 and line 21 to line I9 and thence into fractionation zone 29 for recovery of anhydrous hydrogen fluoride.

The term hydrogen fluoride catalyst as used throughout this specification and appended claims is intended to include those catalysts whose essential active ingredient is hydrogen fluoride. Thus it is within the scope of my invention to have as much as from about to about water present in the hydrogen fluoride alkylation catalyst. Excessive dilution with water, however, is undesirable since it is detrimental to the alkylating activity of the catalyst. It is also within the scope of the invention to have present relatively minor amounts of other diluents, additives, or promoters, for example, boron trifiuoride, which may alter the catalyst activity. In the case of the alkylation of isoparaffins with ethylene it is highly desirable to employ a catalyst containing both hydrogen fluoride and boron trifluoride since hydrogen fluoride alone is not highly effective in this reaction.

The following example is introduced as representative of results which may be attained by the presentinvention although it is not intended to place undue limitations on the generally broad scope of the invention:

In a process substantially as illustrated in the drawing, an isobutane-rich fraction and a C4 hydrocarbon fraction containing about 30 mol per cent of butenes are commingled to form a combined hydrocarbon feed having a molal ratio of isobutane to butenes of 6:1. This charging stock is contacted in a mechanically agitated alkylation zone with a hydrogen fluoride catalyst comprising used catalyst recycled from a separation zone hereinafter described and a small amount of added anhydrous hydrogen fluoride. The catalyst phase contains, on a weight basis, approximately 80% lfree hydrogen nuoride, 2% water and 18% of an organic contaminant or diluent which is formed during the alkylation process. The agitation zone is cooled by suitable means to remove the exothermic heat of reaction and the temperature is maintained at approximately 38 C. under a pressure of about 150 pounds per square inch which is suicient to maintain the catalyst and reactants in substantially the liquid phase. A space time of 30 minutes is utilized.

A portion of the reaction mixture is continuously introduced into a settling zone from which an upper hydrocarbon reaction products layer is withdrawn to a fractionation step wherein alkylation products, normal butane, and light gases are recovered and unconverted isobutane is recatalyst layer is largely recycled yfrom the settling zone to the alkylation zone, but a portion thereof is introduced into a mixing zone wherein suf-y cient water is added to the used catalyst to obf tain an aqueous hydrogenv fluoride solution. con-l taining approximately 70% by weight of' hydro; gen fluoride. The dilution step causes' the organic contaminants in the used catalyst to separate out into a distinct layer which is withdrawn from the system. v n.

The 70% aqueous hydrogen fluoride layer from the dilution step is reacted in a separate mechanically agitated reaction zone with a portion of the C4 hydrocarbon fraction hereinbefore described. This hydrofluorination step is yconducted ata temperature of about 10 C. under suflicient pres,- sure to maintain substantially the liquid phase and in the presence of a substantial molar excess of hydrogen fluoride over butenes. Appreciable amounts of the hydrogen fluoride contained in the aqueous hydrogen fluoride solution are converted to butyl fluorides by reaction withv the butenes in the C4 hydrocarbon fraction. The reaction mixture from the hydro-iiuorination step is introduced into a settling zone, and a hydrocarbon layer comprising essentially unreacted parailins and dissolved butyl fluorides is separated and introduced into the alkylation zone hereinbefore described. The remaining aqueous layer which may contain minor amounts of unconverted hydrogen fluoride is preferably used for diluting the contaminated catalyst in the dilution step hereinbefore described.

In the fractionation of the reaction rproducts, a branched chain isoparailinic alkylate is recovered in a yield of about weight per cent based on the butenes charged to the process. The volumetric ratio of catalyst regenerated alkylate produced j l is approximately 1:20. It will be apparent however that this ratio may be varied within rather broad limits, for example, from about 1:10 to4 about 1:100 dependent uponthe nature of the charging stock, operating conditions, etc; Although this illustration has been described in connection with the alkylation of isobutane with butylenes, it should be apparent that the process is equally applicable to other isoparaiiins and to other oleflns.

I claim as my invention: l

1. In the alkylation of isoparaflinic' hydrocarbons in the presence of a hydrogen fluoride catalyst, the method of regenerating resulting contaminated catalyst which comprises diluting said contaminated catalyst with water to cause separation of a layer of organic contaminants from an aqueous hydrogen fluoride layer, withdrawing said organic contaminants from the sysI tem, reacting said aqueous hydrogen fluoride with olefins to form alkyl fluorides, and return-y tions fdes to the alkylatlon step to cause isoparafilns therein to react with the alkyl fluorides to form alkylated products and to release free hydrogen fluoride ln situ.

3. A process for the alkylatlon of parafllnic hydrocarbons to produce higher molecular weight derivatives thereof which comprises the steps of reacting oleflnic hydrocarbons with lsoparalnic hydrocarbons under alkylating condiin the presence of a hydrogen fluoride caalyst, separating hydrocarbon reaction products from the bulk of the used hydrogen fluoride catalyst, diluting at least a portion of said separated used hydrogen uorlde catalyst with water whereby to separate organic contaminants from aqueous hydrogen fluoride, withdrawing said organic contaminants from the system, reacting at least a portion of said aqueous hydrogen fluoride with oleilnic hydrocarbons under hydrofluorinating conditions whereby to form alkyl fluorides, and introducing said alkyl fiuorides into said flrst named alkylatlon step to produce free hydrogen fluoride by the interaction of said 'isoparafllnlc hydrocarbons and said alkyl halides. y

4. A process for the production of saturated motor fuel which comprises reacting isoparaflinic hydrocarbons with mono oleflns under alkylating conditions in the presence of a catalyst whose essential active ingredient is hydrogen fluoride, separating hydrocarbon reaction products from the bulk of the used hydrogen fluoride catalyst, recycling unconverted isoparafllns to the alkylatlon step, recycling atleast a portion of said separated used hydrogen fluoride catalyst to the alkylatlon step and diluting -another portion with water to cause separation of organic contaminants from aqueous hydrogen fluoride, reacting at least a portion of said aqueous hydrogen flupride with mono oleflnic hydrocarbons under hy'- droiluorinating conditions to form alkyl fluorides, and introducing said alkyl fluorldes into said first named alkylatlon step to produce free hydrogen fluoride by the interaction of said isoparafhnic hydrocarbons with said alkyl halides.

5. In a process for the alkylatlon of lsoparaffinic hydrocarbons wherein oleflns are reacted with hydrogen fluoride under hydrofluorinating conditions in a first stage and the alkyl fiuorides thus formed are then reacted with isoparafllns in a second stage'under alkylating conditions and in the presence of a hydrogen fluoride catalyst, the improvement which comprises employing aqueous hydrogen fluoride containing from about 60 to about 80% by weight of hydrogen fluoride in said hydrofiuorination step whereby to substantially avoid polymerization of oleflns.

6. A process for the alkylatlon of isoparafllnic hydrocarbons which comprises reacting oleflnic hydrocarbons with aqueous hydrogen fluoride containing from about 60 to about 80% by weight of hydrogen fluoride under hydroiluorinating v.conditions in a first reaction zone, recovering alkyl fluorides produced in said first reaction zone and reacting said alkyl iluorides with isoparafnic hydrocarbons under alkylating conditions in the presence of a hydrogen fluoride catalyst containing not more than about by weight of water in a second reaction zone, separating alkylatlon reaction products from the bulk of the used hydrogen fluoride catalyst, recycling at least a portien of said separated used hydrogen fluoride catalyst to the alkylatlon step, diluting another portion of said separated used hydrogen fluoride catalyst with water to cause separation of a layer of organic contaminants from aqueous hydrogen fluoride, withdrawing said organic contaminants another portion of said used hydrogen fluoride.

catalyst with water whereby to separate organic contaminants from aqueous hydrogen fluoride, converting said aqueous hydrogen uorlde to alkyl fluorides by reacting it with oleflnic hydrocarbons under hydrofiuorinating conditions in a separate reaction zone, recovering alkyl uorides from the reaction mixture, and introducing said alkyl fluorides into said alkylatlon step.

8. A process for the alkylatlon of parafllnic hydrocarbons to produce higher molecular weight derivatives thereof which comprises reacting oleflnic hydrocarbons with isoparafllnic hydrocarbons under alkylating conditions in the presence of a hydrogen fluoride catalystfseparating hydrocarbon reaction products from the bulk of the used hydrogen fluoride catalyst, diluting at least a portion of said separated used hydrogen uoride catalyst with water whereby to separate organic contaminants from aqueous hydrogen fluoride, withdrawing said organic contaminants from the system, reacting at least a portion of said aqueous hydrogen fluoride with olenic hydrocarbons under hydrofluorinatlng conditions to form alkyl fluorides, separating alkyl fluorides and unconverted hydrocarbons from an aqueous layer, lntroducing said alkyl fluorides into said first named alkylatlon step to produce free hydrogen fluoride derivatives thereof which comprises reacting oleflnic hydrocarbons with isoparafllnic hydrocarbons under alkylating conditions in the presence of a hydrogen fluoride catalyst, separating hydrocarbon reaction products from the bulk of the used hydrogen fluoride catalyst, diluting at least a portion of said separated used hydrogen fluoride catalyst with water to separate organic contaminants from aqueous hydrogen fluoride and withdrawing said organic contaminants from the system, reacting at least a portion of said aqueous hydrogen fluoride with olefinic hydrocarbons under hydrofluorinating conditions to form alkyl fluorides, introducing said alkyl fluorides into said alkylatlon step, introducing another portion of said aqueous hydrogen fluoride into a fractionation zone wherein substantially anhydrous hydro- -gen fluoride is separated overhead from a. bottoms product comprising a mixture of hydrogen fluoride and water and returning said anhydrous hydrogen fluoride to the alkylatlon step.

10. A process for the alkylatlon of paraflinic hydrocarbons to produce higher molecular weight derivatives thereof which comprises reacting oleilnic hydrocarbons with isoparafnnic hydrocarbons under alkylating conditions in the presence of a hydrogen iluorlde catalyst, separating hydrocarbon reaction products from the bulk of the used hydrogen fluoride catalyst, diluting at least a portion of said separated used hydrogen fluoride catalyst with water whereby to separate organic contaminants from aqueous hydrogen fluoride, reacting at least a portion of said aqueous hydrogen fluoride with oleiinic hydrocarbons under hydroiiuorinating conditions to form alkyl fiuorides, separating said alkyl fluori-des and unconverted hydrocarbons from an aqueous layer, introducing said alkyl iiuorides into said first named alkylation step, returning at least a portion of said last named aqueous layer to the aforesaid dilution, subjecting another portion of said iirst named aqueous hydrogen fluoride to fractionation whereby anhydrous hydrogen iiuoride is separated overhead from a mixture of hydrogen fluoride and water, returning said anhydrous hydrogen iluoride to the alkylation step, and introducing another portion of said aqueous layer from said hydrouorination step to said fractionation step.

11. The process of claim 9 wherein at least a portion of said substantially anhydrous hydrogen iiuoride from said fractionation step is introduced into said hydroiluorination step.

12. The process of claim 9 wherein a portion of said anhydrous hydrogen uoride is introduced into said alkylation zone and another portion thereof is introduced into said hydrofluorination zone.

13. The process of claim 9 wherein the bottoms product from said fractionation step comv prises a constant boiling mixture of hydrogen catalyst whose essential active ingredient is hy drogen fluoride at a temperature of from about -30 to about 100 C. under sufficient pressure t0 maintainthe reactants and catalyst in substantially the liquid phase, separating hydrocarbon reaction products from the bulk of the used hydrogen fluoride catalyst, subjecting said hydrocarbon reaction products to fractionation to separate desired alkylation products from unconverted hydrocarbons and light gases, recycling unconverted isoparafiins to the alkylation step, recycling at least a portion of said separated used hydrogen fluoride catalyst to the alakylation step, diluting another portion of said separated used hydrogen fluoride catalyst with water to separate organic contaminants from aqueous hydrogen fluoride, reacting at least a portion of said aqueous hydrogen fluoride with mono oleflnic hydrocarbons at a temperature of from about -30 to about 100 C. under sumcient pressure to maintain the reactants in substantially the liquid phase and in the presence of a substantial molar is reacted with pentene in said alkylation step.

18. The process of claim 1 wherein said contaminated catalyst is diluted with suilicient water to form aqueous hydrogen fluoride containing from about to about 80% by weight of hydrogen fluoride.

` CARL B. LINN. 

